nRF5340 shockburst software CRC calculation

RE: nRF5340 shockburst software CRC calculation

ubat — Tue, 05 Jul 2022 15:11:54 GMT

It's working now, thanks to Kenneth. Using the SPI data order of the nRF2401 did the trick.

For a bit-wise C implementation of the employed CRC one can e.g. use this one c - CRC bit-order confusion - Stack Overflow

RE: nRF5340 shockburst software CRC calculation

ubat — Tue, 05 Jul 2022 11:53:26 GMT

Thank you! So the nRF2401 SPI has got the same bit-order as on-air, that's good to know! We do have a VHDL code for that, so i will go by that.

Most CRC calculators go byte-wise, yup - using a bit-wise shift-register approach like in a FPGA here 🙂

Best regards,

Uli

RE: nRF5340 shockburst software CRC calculation

Kenneth — Tue, 05 Jul 2022 09:41:29 GMT

Only the address and payload is calculated in this case yes. The order is the order the bits are sent on-air for both address and payload (the easiest may be to just connect a logic analyzer to the SPI pins of the nRF2401 to check the bit order, both the address and payload are clocked in for each transmission from the nRF2401). If you are using 95-bits for the payload, I assume this becomes difficult to calculate, at least with various crc calculators online due to the non-byte aligned bitstream.

Best regards,
Kenneth

RE: nRF5340 shockburst software CRC calculation

ubat — Mon, 04 Jul 2022 14:21:47 GMT

Small corrigendum: "Our payload length is 95 bit."